a.1.(Chem.) Applied to an acid having in each molecule two atoms of sulphur in the higher state of oxidation.
Disulphuric acid
a thick oily liquid, H2S2O7, called also Nordhausen acid (from Nordhausen in the Harts, where it was originally manufactured), fuming sulphuric acid, and especially pyrosulphuric acid. See under Pyrosulphuric.